Alternating pressure air mattresses as prevention for pressure ulcers: a literature review

Vanderwee K, Grypdonck M, Defloor T

CRD summary

The authors concluded that alternating pressure air mattresses were likely to be more effective than standard hospital mattresses, but no conclusions could be reached about their comfort and further research was required. The authors’ conclusions appeared to reflect the evidence, but incomplete reporting of review methods and any differences between studies made it difficult to assess their reliability.

Authors' objectives

To examine studies evaluating alternating pressure air mattresses for the prevention of pressure ulcers.

Searching

PubMed/MEDLINE, CINAHL, EMBASE and Cochrane Central Register of Controlled Trials were searched from 1980 to September 2006 for studies published in English, German, French or Dutch. Search terms were reported. In addition, reference lists of retrieved articles were screened.

Study selection

Studies of any design that compared alternating pressure air mattresses (APAMs) with other mattresses or other types of alternating pressure air mattresses for the prevention of pressure ulcers were eligible for inclusion. In the review, alternating pressure air mattresses were defined as alternating pressure air replacements (APARs) and alternating pressure air overlays (APAOs). The review assessed effectiveness, contact interface pressure and blood perfusion, comfort, mechanical reliability and costs.

Randomised controlled trials in a variety of patients (at-risk, surgical, long-term care elderly, geriatric, chronic medical conditions, orthopaedic and intensive care unit) and experimental laboratory studies in predominantly healthy people were included. Studies compared different types of alternating pressure air mattresses with each other and with a variety of other types of mattresses (including air, water, foam, gel, hollow fibre, constant low-pressure and standard hospital mattresses). Studies used the following methods to assess effectiveness: the incidence of pressure ulcers; contact interface pressure (CIP); and blood perfusion, as measured by transcutaneous oxygen (tcPO2) and transcutaneous carbon dioxide (tcPCO2). Comfort was generally assessed using non-validated questionnaires or visual analogue scales. Where reported, the duration of follow-up among randomised controlled trials assessing effectiveness ranged from one week to three months.

Two reviewers independently selected studies.

Assessment of study quality

The validity of randomised controlled trials was assessed using power calculation, reporting of randomisation method and baseline comparability of treatment groups. Other methodological limitations assessed included drop-outs and unit of analysis. The authors did not state how the validity assessment was performed.

Data extraction

The authors stated neither how data were extracted for the review nor how many reviewers performed the data extraction. For each study, results data for the main outcomes were reported with some indication of the level of statistical significance.

Methods of synthesis

The studies were grouped by outcome and study design and combined in a narrative synthesis. Data were presented in tables.

Study quality: 18 randomised controlled trials either had insufficient power or did not estimate the required sample size; 11 randomised controlled trials had unclear or inadequate randomisation; and four randomised controlled trials did not report baseline comparability of treatment groups. The sample size of laboratory studies was small (10 to 57) and nine such studies involved only healthy people.

Comfort: Four randomised controlled trials compared alternating pressure air mattresses with constant low-pressure mattresses. Studies variously reported problems with hardness and noise (one study), few problems with either mattress (one study), no significant difference in comfort scores (one study) and more problems with alternating pressure air overlays compared to alternating pressure air replacements (one study). The authors stated that findings on comfort were inconsistent due to different types of mattresses used and outcomes reported. Results from other laboratory studies and randomised controlled trials that compared different types of alternating pressure air overlays were also reported.

Mechanical reliability and user errors were also reported in the review.

Cost information

One cost-effectiveness study reported that alternating pressure air overlays were more cost-effective than standard hospital mattresses for the prevention of pressure sores. Other studies reported increased costs with alternating pressure air overlays compared with hollow fibre mattresses (54 per cent increase in one study) and lower costs with alternating pressure air replacements, mainly due to reduced length of stay and delayed development of pressure sores (one study).

Authors' conclusions

Alternating pressure air mattresses were likely to be more effective than standard hospital mattresses, but no conclusions could be reached about their comfort. Further research was required.

CRD commentary

The review question was clearly stated. Inclusion criteria were defined for intervention and outcomes. Criteria for study design were broad. No criteria were defined for participants. Several relevant sources were searched and some attempts were made to reduce language bias. No attempts to minimise publication bias were reported. Methods were used to minimise reviewer errors and bias in the selection of studies, but it was unclear whether similar steps were taken in the assessment of validity and data extraction. The validity of randomised controlled trials was assessed and the results were reported. In view of the diversity among studies, a narrative synthesis was appropriate. The authors’ conclusions appeared to reflect the evidence, but incomplete reporting of review methods and any clinical and methodological differences between studies made it difficult to interpret the evidence and, therefore, the reliability of the authors' conclusions.

Implications of the review for practice and research

Practice: The authors stated that health organisations must ensure that nurses were trained in the correct use of different alternating pressure air mattresses. The authors were unable to make recommendations for clinical practice about the efficacy of different alternating pressure air mattresses or alternating pressure air mattresses compared to constant low-pressure mattresses.

Research: The authors stated that large high-quality randomised controlled trials were required to evaluate the effectiveness of alternating pressure air mattresses. There was a need to design and validate more appropriate measures of comfort.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.